Warnings appear in tomcat/logs/catalina.out about log4j, such as:
log4j:WARN No appenders could be found for logger (net.bull.javamelody). log4j:WARN Please initialize the log4j system properly.
You just need to properly configure
log4j.xml. One of these files should exist in
/WEB-INF/classes. If not create them.
Navigate here to the section Configuration to see what to include in this file: Apache log4j manual
One of the examples from that link for
# Set root logger level to DEBUG and its only appender to A1. log4j.rootLogger=DEBUG, A1 # A1 is set to be a ConsoleAppender. log4j.appender.A1=org.apache.log4j.ConsoleAppender # A1 uses PatternLayout. log4j.appender.A1.layout=org.apache.log4j.PatternLayout log4j.appender.A1.layout.ConversionPattern=%-4r [%t] %-5p %c %x - %m%n